The common cold is a major worldwide health problem. It has been reported that during a recent year common colds occurred in the United States an average of 3.9 times per person and led to an average restriction in activity of 1.2 days per person. The magnitude of the problem is apparent. Losses in productivity, expenditures for so-called "cold remedies" and doctor visits, complications such as sinusitis, and the human misery involved make the common cold a major public health problem.
Little progress has been made toward controlling or curing the common cold. Virtually all new products dealing with the common cold are directed toward relieving the symptoms. And, prevention and/or cure of viral respiratory infections by the usual means--vaccination and chemotherapy--seem out of reach at present.
The large number of respiratory infection virus types make a respiratory infection virus vaccine appear, at present, to be unlikely at best. Rhinoviruses are the principal common cold viruses. There are about 110 different rhinovirus types alone, as well as the influenza and parainfluenza viruses, respiratory syncytial viruses, coronaviruses, and others.
Chemotherapy and chemoprophylaxis do not offer a practical answer either since, at present, there are no practical agents useful against the common cold. Large doses of ascorbic acid, which have been advocated for both prevention and treatment of the common cold, have not been shown effective; the results of controlled experiments have been equivocal at best.
A major obstacle for vaccines or chemical treatments against the common cold is that, unlike many other diseases, both virus acquisition and the disease process occur on the respiratory mucosal surfaces. While this fact may make the common cold difficult to prevent and cure, it has widely been thought that it makes the common cold very easy to transmit and that transmission occurs in many ways. However, in recent years, considerable evidence has been collected showing that respiratory viral infections are much more difficult to spread than was commonly believed.
Various experiments have shown that, generally speaking, only those persons who have relatively severe colds and are shedding rather large amounts of virus seem capable of transmitting their infections to others. Although it is common for physicians and their patients to think of respiratory illnesses as being very contagious, studies have shown that transmission may be surprisingly difficult unless there is considerable intimacy. It was found that inter-family spread was very sporadic, while intra-family dissemination of respiratory viruses was more likely.
Substantial data have shown that infection is likely to occur by contact self-inoculation, that is, the transfer of viruses from a person's virus-contaminated fingers to his own nasal or conjunctival surfaces. This is a process which seems more likely to occur in situations in which there is considerable intimacy or prolonged association. Rhinovirus contamination of hands occurs frequently during rhinovirus colds and it has been shown that rhinoviruses survive well on skin and environmental surfaces. Finger-to-nose and finger-to-eye movements are performed frequently, either consciously or unconsciously, by both adults and children, and these actions are capable of initiating infection if the fingers were previously contaminated.
Transmission is likely to occur, for example, when a parent grossly soils his hands with nasal effluent while wiping the nose of a child and later contaminates his own nasal mucosa or conjunctiva by self-inoculation. Transmission can also occur if an infected family member contaminates his fingers by contact near or insertion into his nares, and then such contamination either directly or indirectly reaches the fingers of a healthy family member who thereafter inserts them into his own nares or with them contacts his conjunctivas.
The developments over the last several years have led to a recognition that the spread of respiratory viral infections may be interruptable more easily than had previously been believed, by eliminating infectious viruses from hands and environmental surfaces to reduce the self-inoculation which otherwise would occur during conscious or unconscious hand movements. It has been noted that infectious viruses could be eliminated from the hands by more frequent hand washing. Frequent hand washing could be specifically promoted for those having colds, particularly after coughing, sneezing, or attending to the profuse nasal discharge that may accompany common colds.
However, avoiding or significantly reducing the conscious or unconscious hand-to-face motions that are so common presents a difficult, if not insurmountable, problem. Even though hand washing might be frequent, the normal hand-to-face movements will continue to cause the frequent transmission of respiratory viral infections through the spread of virus from the infected person and the self-inoculation of the healthy person.